# Cold exposure induces the constitutively active thermogenic receptor, GPR3, via ERRα and ERRγ

## TL;DR

Cold exposure activates the GPR3 receptor in fat cells through ERRα and ERRγ, which could help increase energy expenditure and treat obesity.

## Contribution

The study identifies ERRα and ERRγ as key regulators of GPR3 transcription in response to cold exposure.

## Key findings

- The Gpr3 promoter contains differentially accessible ERR elements in BAT in mice exposed to cold.
- ERRα binds to the Gpr3 promoter and activates it with PGC-1α in vitro.
- ERRα and ERRγ are required for cold-induced Gpr3 transcription in vivo.

## Abstract

Despite transformative advances in obesity pharmacotherapy, safely increasing energy expenditure remains a key unmet need. Exploiting thermogenic adipocytes represents a promising target given their capacity for significant catabolic activity. We previously showed that G protein-coupled receptor 3 (GPR3) can drive energy expenditure in brown and white mouse and human adipocytes. GPR3 is a unique GPCR because it displays high intrinsic activity and leads to constitutive cAMP signaling upon reaching the cell surface. Therefore, the transcriptional induction of GPR3 is analogous to ligand-binding activation of most GPCRs. Gpr3 expression is physiologically induced in thermogenic adipocytes by cold exposure, and mimicking this event through overexpression in mice is fully sufficient to increase energy expenditure and counteract metabolic disease. Yet the factors mediating physiological Gpr3 expression remain unknown.

Here, we apply ATAC-Seq to identify cold-induced promoter elements of Gpr3. We uncover a role for the estrogen-related receptors, ERRα and ERRγ, in the physiological transcriptional control of Gpr3 using adipose-specific double knock-out mice with and without adeno-associated virus (AAV)-mediated rescue.

We show that ERRα directly binds the cold-induced promoter element of Gpr3 and that ERRα, ERRβ, and ERRγ each activate the Gpr3 promoter in vitro when co-transfected with PGC-1α. Adipocyte ERRα and ERRγ are required for the in vivo transcriptional induction of Gpr3 during cold exposure. Importantly, deficient Gpr3 cold-inducibility in adipose-specific ERRα and ERRγ KO mice is fully rescued by delivery of AAVs re-expressing either ERRα or ERRγ directly into brown adipose tissue.

ERRα and ERRγ are critical regulators of cold-induced transcription of Gpr3 and represent a targetable strategy for pharmacologically unlocking GPR3-induced energy expenditure.

•The Gpr3 promoter contains differentially accessible ERR elements in BAT in mice exposed to cold.•ERRα binds to the Gpr3 promoter.•Cold-inducibility of Gpr3 is fully dependent on ERRα and ERRγ in vivo.

The Gpr3 promoter contains differentially accessible ERR elements in BAT in mice exposed to cold.

ERRα binds to the Gpr3 promoter.

Cold-inducibility of Gpr3 is fully dependent on ERRα and ERRγ in vivo.